The present invention is related generally to primary electrochemical cells and is more particularly concerned with a novel construction for such cells which results in an ultrathin compact configuration.
Primary electrochemical cells are utilized for a wide variety of applications and are commonly available in a significant assortment of sizes and shapes. One such application which is of continuing importance is the incorporation of a power source into electronic watches. Such power sources are required to supply a low current over an extended period of time. Primary electrochemical cells are available which perform this function; however, the commercially available cells suffer from one or more disadvantages which preclude complete freedom to the designer of the watches. Firstly, the discharge capacity of the cell needed to provide an acceptable useful life limits the size to which the cell may be reduced. Typically, it is required that the cells power the watch for a minimum of one year. Secondly, the cell configurations which have been available are sufficiently bulky as to dictate the configuration that the watch casing may take, particularly with regards to thickness.
Typically, a total thickness of approximately 5 millimeters has been required for prior art button cells. Although the thickness of all cell components could theoretically be reduced to achieve a thinner cell, the structural limitation of approximately 5mm is predominately imposed by the rigidity of the cell cathode. Conventional cathode materails are rigid structures incapable of absorbing the flexing of the thinner cell containers. The rigidity has been attributable to the need for physical contact between a maximum number of cathodic particles to yield the requisite conductivity and mechanical strength.
U.S. Pat. No. 3,852,115 to Richard W. Lewis et al. discloses a button type cell in which alkaline electrolyte is mixed in with a zinc amalgam anode material which is separated from the cathode assembly by one or more plastic microporous separators.
U.S. Pat. No. 3,666,560 to Elton J. Cairns et al. discloses a cell in which an electrolyte in the form of a paste disc is sandwiched between the anode and the cathode.
U.S. Pat. No. 3,907,593, assigned to the assignee of this application, discloses a button type cell in which a liquid electrolyte is in a compartment sandwiched between the cathode and anode and separated from the cathode by a spacer.
Other cell arrangements may be found in U.S. Pat. No. 2,812,377 to John V. Franquemont, U.S. Pat. No. 3,853,627 to Gerard Lehmann et al., U.S. Pat. No. 3,880,672 to El Sayed Megaked et al. and U.S. Pat. No. 3,920,478 to Kozawa.